Question

There are 10 girls and 20 boys in a class.

The class has a test.

The mean mark for all the class is 70
The mean mark for all the boys is 62

Work out the mean mark for the girls.

Answer 1

86

Explanation:

mean is calculated as

mean =
`(sum)/(count)`

given mean mark for class of 30 is 70 , then

`(sum)/(30)` = 70 ( multiply both sides by 30 )

sum = 2100

given the mean mark for 20 boys is 62, then

`(sum)/(20)` = 62 ( multiply both sides by 20 )

sum = 1240

the sum for the 10 girls is then 2100 - 1240 = 860

then mean score for the 10 girls is

mean =
`(860)/(10)` = 86